Sulphur and nitrogen content as sulphur deficiency indicator for grasses

In Europe, during the last 30 years, the decrease in sulphur (S) atmospheric depositions has led to S deficient grasslands. Concern for S fertilisation resulted in research about S fertilisation advices and definition of S nutritional diagnostic tools for plants. However, for grasses, S nutrition indicators are still discussed. We propose a diagnostic tool based upon linear relationships linking the sulphur and nitrogen (N) content of grasses. This diagnostic tool is built thanks to data from field and pot trials treated with an algorithm (Bolides) and discriminant analyses. The relationships allow the characterisation of the grass sulphur nutritional status following four categories: certainly sufficient, probably sufficient, probably deficient and certainly deficient. This relation based and tested on a large dataset from literature and own field trials allowed diagnosing correctly 94% of the sulphur sufficient grasses and 71% of the sulphur deficient grasses.